1. Field of the Invention
Microorganisms which are capable of producing metabolic products and proteins are becoming increasingly important in industry in such diverse fields as production of industrial chemicals, dairy products, antibiotics and in industrial applications.
Microorganisms can be obtained by routine screening of soil samples; by classical genetic manipulation techniques, e.g., ultraviolet irradiation and mutation selection; or by recombinant DNA technology involving the transfer of genetic material from one microorganism into a host microorganism to alter the genetic characteristics of the host microorganism.
In each case, a series of microorganisms must be screened in order to detect a microorganism which has the desired characteristic. Such screening and isolation of microorganisms usually involves growing and examining a large number of colonies of microorganisms and is labor intensive and time-consuming.
2. Description of the Prior Art
The detection and isolation of a microorganism having a desired genetic trait or which produces a desired substance involves the steps of growing the microorganism on a suitable agar medium and using some technique for detecting the desired microorganism. The desired microorganism is then removed from colonies of other microorganisms, and isolated.
In some bacterial strains a means for "primary" selection exists, e.g., if the desired microorganism is resistant to a certain antibiotic, the microorganisms to be examined can be cultured in the presence of such antibiotic and the microorganisms which survive can be selected and isolated. In contrast, some microorganisms do not carry a "primary" selection trait. Such microorganisms must be screened and isolated by means of biochemical tests, referred to as "screening" techniques. For example, microorganisms which produce the enzyme alpha(.alpha.)-amylase, can be screened by incorporating starch in an agar medium, growing the microorganisms, contacting the agar with iodine and observing the agar for clear zones, which indicate the presence of starch hydrolysis caused by an .alpha.-amylase secreting microorganism.
Examination of microorganisms grown in an agar medium involving either a primary selectable trait or a biochemical screening test is laborious and time-consuming by conventional techniques. Standard assays exist which can be applied to a relatively small number of colonies growing on an agar plate.
There is a need for an improved method for detecting a desired microorganism. It is therefore an object of the present invention to provide a rapid and economical means for examining a large number of microorganisms growing in an agar medium and selecting a microorganism producing a desired substance, using a small number of manipulative steps and materials.